Quantum state preparation for trapped-ion qubits often relies on high-quality circularly polarized light, which may be difficult to achieve with chip-based integrated optics technology. We propose and implement a hybrid optical and microwave scheme for intermediate-field hyperfine qubits which instead relies on frequency selectivity. Experimentally, we achieve 99.94 % fidelity for linearly polarized ( σ + / σ − ) light, using Ca + 43 at 28.8 mT. We find that the fidelity remains above 99.8 % for a mixture of all polarizations ( σ + / σ − / π ) . We calculate that the method is capable of 99.99 % fidelity in Ca + 43 , and even higher fidelities in heavier ions such as Ba + 137 . Published by the American Physical Society 2024Quantum state preparation for trapped-ion qubits often relies on high-quality circularly polarized light, which may be difficult to achieve with chip-based integrated optics technology. We propose and implement a hybrid optical and microwave scheme for intermediate-field hyperfine qubits which instead relies on frequency selectivity. Experimentally, we achieve 99.94 % fidelity for linearly polarized ( σ + / σ − ) light, using Ca + 43 at 28.8 mT. We find that the fidelity remains above 99.8 % for a mixture of all polarizations ( σ + / σ − / π ) . We calculate that the method is capable of 99.99 % fidelity in Ca + 43 , and even higher fidelities in heavier ions such as Ba + 137 . Published by the American Physical Society 2024

arXiv:2406.14448Physical Review AOct 16, 20242 citations

High-fidelity operation of a radioactive trapped-ion qubit, $^{133}$ Ba $^+$ High-fidelity operation of a radioactive trapped-ion qubit, $^{133}$Ba$^+$

Justin Christensen

$^{133}$ Ba $^+$ has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-1/2 nucleus, visible wavelength electronic transitions, and long D-state lifetimes ($\\tau\\sim $1~min). Using a microgram source of radioactive material, we trap and laser-cool the synthetic \\textit{A} = 133 radioisotope of barium II ($ \\tau_{1/2} \\approx 10.5 $~yr) in a radio-frequency ion trap. To demonstrate high fidelity qubit operations, a number of unknown state energies were needed. We measure the isotope shift and hyperfine structure of the 6$ ^2 $P$ _{1/2}\\leftrightarrow 5^2 $D$ _{3/2}$ electronic transition needed for laser cooling, state preparation, and state detection of the clock-state hyperfine and optical qubits. For high-fidelity operations with electron shelving, we report measurements of the 6 $^2$ P $_{3/2}$ and $5^2$ D $_{5/2}$ hyperfine splittings, as well as the~6 $^2$ P $_{3/2}~\\leftrightarrow~6^2$ S $_{1/2}$ and ~6 $^2$ P $_{3/2}~\\leftrightarrow~5^2$ D $_{5/2}$ transition frequencies. Using these transitions, we demonstrate high-fidelity \\ba \\ hyperfine qubit manipulation with electron shelving detection to benchmark qubit state preparation and measurement (SPAM). Using single-shot, threshold discrimination, we measure an average SPAM fidelity of $\\mathcal{F} = 0.99971(3)$ , a factor of $\\approx$ 2 improvement over the best reported performance of any qubit.Finally, we report the 6 $^2$ P $_{1/2}\\leftrightarrow 5^2$ D $_{3/2}$ electronic transition isotope shift for the rare \\textit{A} = 130 and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes.$^{133}$Ba$^+$ has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-1/2 nucleus, visible wavelength electronic transitions, and long D-state lifetimes ($\\tau\\sim $1~min). Using a microgram source of radioactive material, we trap and laser-cool the synthetic \\textit{A} = 133 radioisotope of barium II ($\\tau_{1/2} \\approx 10.5$~yr) in a radio-frequency ion trap. To demonstrate high fidelity qubit operations, a number of unknown state energies were needed. We measure the isotope shift and hyperfine structure of the 6$^2$P$_{1/2}\\leftrightarrow 5^2$D$_{3/2}$ electronic transition needed for laser cooling, state preparation, and state detection of the clock-state hyperfine and optical qubits. For high-fidelity operations with electron shelving, we report measurements of the 6$^2$P$_{3/2}$ and $5^2$D$_{5/2}$ hyperfine splittings, as well as the~6$^2$P$_{3/2}~\\leftrightarrow~6^2$S$_{1/2}$ and ~6$^2$P$_{3/2}~\\leftrightarrow~5^2$D$_{5/2}$ transition frequencies. Using these transitions, we demonstrate high-fidelity \\ba \\ hyperfine qubit manipulation with electron shelving detection to benchmark qubit state preparation and measurement (SPAM). Using single-shot, threshold discrimination, we measure an average SPAM fidelity of $\\mathcal{F} = 0.99971(3)$, a factor of $\\approx$ 2 improvement over the best reported performance of any qubit.Finally, we report the 6$^2$P$_{1/2}\\leftrightarrow 5^2$D$_{3/2}$ electronic transition isotope shift for the rare \\textit{A} = 130 and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes.

Jan 1, 20203 citations

Single qubit manipulation in a microfabricated surface electrode ion trap

Emily Mount, So-Young Baek, Matthew Blain +7 more

We trap individual 171 Yb + ions in a surface trap microfabricated on a silicon substrate, and demonstrate a complete set of high fidelity single qubit operations for the hyperfine qubit. Trapping times exceeding 20 min without laser cooling, and heating rates as low as 0.8 quanta ms −1 , indicate stable trapping conditions in these microtraps. A coherence time of more than 1 s, high fidelity qubit state detection and single qubit rotations are demonstrated. The observation of low heating rates and demonstration of high quality single qubit gates at room temperature are critical steps toward scalable quantum information processing in microfabricated surface traps.We trap individual 171 Yb + ions in a surface trap microfabricated on a silicon substrate, and demonstrate a complete set of high fidelity single qubit operations for the hyperfine qubit. Trapping times exceeding 20 min without laser cooling, and heating rates as low as 0.8 quanta ms −1 , indicate stable trapping conditions in these microtraps. A coherence time of more than 1 s, high fidelity qubit state detection and single qubit rotations are demonstrated. The observation of low heating rates and demonstration of high quality single qubit gates at room temperature are critical steps toward scalable quantum information processing in microfabricated surface traps.

arXiv:1306.1269New Journal of PhysicsSep 13, 201341 citations

Experimental demonstration of high fidelity

{}^{133}

^+

hyperfine qubits

Preparation and detection of a

^{137}

^{+}

hyperfine qubit

Ultra-High Fidelity Operation of the

^{133}

^+

qubit

Demonstration of an optical qubit in

^{137}

^{+}

ions

High-fidelity operation of a radioactive trapped-ion qubit,

^{133}

^+

^{133}

^+

has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-1/2 nucleus, visible wavelength electronic transitions, and long D-state lifetimes ($\\tau\\sim

1~min). Using a microgram source of radioactive material, we trap and laser-cool the synthetic \\textit{A} = 133 radioisotope of barium II (

\\tau_{1/2} \\approx 10.5

~yr) in a radio-frequency ion trap. To demonstrate high fidelity qubit operations, a number of unknown state energies were needed. We measure the isotope shift and hyperfine structure of the 6

P

_{1/2}\\leftrightarrow 5^2

D

_{3/2}$ electronic transition needed for laser cooling, state preparation, and state detection of the clock-state hyperfine and optical qubits. For high-fidelity operations with electron shelving, we report measurements of the 6

^2

_{3/2}

and

5^2

_{5/2}

hyperfine splittings, as well as the~6

^2

_{3/2}~\\leftrightarrow~6^2

_{1/2}

and ~6

^2

_{3/2}~\\leftrightarrow~5^2

_{5/2}

transition frequencies. Using these transitions, we demonstrate high-fidelity \\ba \\ hyperfine qubit manipulation with electron shelving detection to benchmark qubit state preparation and measurement (SPAM). Using single-shot, threshold discrimination, we measure an average SPAM fidelity of

\\mathcal{F} = 0.99971(3)

, a factor of

\\approx

2 improvement over the best reported performance of any qubit.Finally, we report the 6

^2

_{1/2}\\leftrightarrow 5^2

_{3/2}

electronic transition isotope shift for the rare \\textit{A} = 130 and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes.